The unexamined patent application DE102004057296 A1 discusses a driver assistance device for warning a driver of a motor vehicle of an imminent departure from the roadway or a departure from the lane. The device includes at least one imaging sensor, an evaluation device connected to the imaging sensor for detecting roadside markings and/or lane markings and/or edges of lanes in the area detected by the imaging sensor, as well as a warning device, which is connected to the evaluation device.
In such systems, the departure from a lane is detected with the aid of a video camera, based on lane markings or lane boundaries, for example, based on a curbside. The driver is warned when he/she unintentionally departs from the lane.
The warning may be triggered based on two variables: DLC (distance to line crossing) or TLC (time to line crossing). One problem in triggering via the variable DLC, via the distance of the vehicle to the lane boundary, is that the driver is variously warned depending on how fast the vehicle drifts to the boundary. Latencies in the overall vehicle system of several hundred microseconds result in a warning—for example, a sound signal or a vibration of a steering wheel—which is late or delayed in reaching the driver. If the vehicle drifts rapidly away, it may be that the warning occurs only when the vehicle has already crossed the lane boundary.
In the second approach TLC (time to line crossing), in which the time until the lane boundary is crossed is used, the warning point in time is adjusted as a function of the lateral velocity. In these calculations, the curvature of the lane is in part not taken into consideration. It may be that as a result, the warning for the inside of the curve is often triggered too late and the warning for the outside of the curve is often triggered too early.